Hygrostat apparatus



Sept. 20, 1960 v. vAlsALA HYGROSTAT APPARATUS Filed May 13, 1958 b 1 5 Ili HYGROSTAT APPARATUS Vilho Vaisiilii, Mantyfie A, Helsinki, Finland Filed May 13, 1958, Ser. No. 734,934

Claims priority, application Finland May 15, 1957 7 Claims. (Cl. 1834.3)

The present invention relates to a new and novel hygrostat apparatus, and more particularly to a hygrostat apparatus employing a novel mixing valve for producing varying degrees of humidity.

In certain applications, it is desirable to produce gaseous mixtures such as air of a specified humidity. For example, it has been found necessary to calibrate the hygroscopic hygrometers used in radiosondes at a minimum of three humidity values in order to obtain satisfactory results. It is apparent that in such calibration procedures, it is necessary to produce air of a predetermined humidity with a high degree of accuracy and reliability in order to properly calibrate such delicate instruments.

Many attempts have been made in the prior art to produce apparatus for this purpose, but these have proven to be unsatisfactory for a variety of reasons. In some apparatuses the humidity is controlled by means of salt solutions utilized in the channel where the air is circulated. Separate containers having the various salt solutions therein must be inserted and removed from the apparatus each time it is desired to alter the humidity, and accordingly this procedure is very time consuming. In addition, this method is not suitably accurate due to the difficulty in reproducing the proper salt solution each time the apparatus is operated, and further the structure is necessarily bulky and relatively complicated. Other prior art structures suffer from the same disadvantages.

The present invention is constructed in accordance with the principle that in calibrating a hygroscopic hygrometer, only a minute speed of ventilation is required to create hygroscopic equilibrium. Accordingly only small quantities of air are required to provide the desired degree of humidity for calibration, and it is not necessary to produce a rapid flow of air. Consequently, the apparatus of the invention is open at opposite ends thereof thereby utilizing the air of the room in which it is operated.

In accordance with the present invention, the apparatus is constructed such that the incoming air is divided into two paths whereupon a portion of the incoming air passes through a drying chamber and a portion passes through a moistening chamber. These chambers are provided with simple and efiicient means for respectively drying and moistening the air. The air is then conducted to a new and novel mixing valve where the dry and moist air are combined and subsequently conducted to an outlet means wherein the hygrometers to be calibrated may be mounted, for example.

The mixing valve of the invention is provided with a plurality of openings in communication with each of the drying and moistening chambers. These openings are so constructed and arranged that the humidity of the air in the outlet means may be quickly and efficiently adjusted while maintaining the same number of openings in communication with each of the chambers at all times. In this maner, the air flow through the two chambers remains constant during operation which is very desirable.

Patented Sept. 2-0,; 1960 ice It is apparent that the present invention is not restricted to the testing of hygrometers, but may be employed in any application where it is desired to produce varying degrees of humidity.

An object of the present invention is to provide a new and novel hygrostat device wherein the humidity of the outlet air may be quickly and efliciently adjusted.

Another object is the provision of a hygrostat device wherein the adjustments required during operation of the device are reduced to a minimum.

Yet another object is to provide a hygrostat device which is simple and inexpensive in construction, yet accurate and reliable in operation.

Other objects and many of the attendant advantages of the present invention will become apparent when considered in connection with the specification and accompanying drawing wherein:

Fig. 1 is a longitudinal elevational section of the device; and

Fig. 2 is a cross-sectional view of the device shown in Fig. 1 taken along the line IIlI looking in the direction of the arrows.

Referring now to the drawing wherein like reference nrnnerals denote like parts in the various views, an inlet conduit 10 is provided with a blower in the form of a fan 11, for example, for forcing air through the apparatus. It is of course feasible to also draw air through the apparatus by providing a fan at the opposite end thereof, but the arrangement shown is considered preferable because the excess pressure generated prevents any undesirable mixing of air from the room with the air in the apparatus. Fan 11 is driven by a pulley 12 connected by belt 13 to a second pulley 14 which is driven by an electric motor 15 or the like.

Inlet conduit 1!] opens into a dividing chamber 20 where the incoming air is divided into two paths flowing through openings 21 and 22 therefrom. Opening 21 provides communication with the interior of a drying chamber 23, and opening 22 provides communication with the interior of a moistening chamber 24. In the drying chamber 21 three drying units 25, each of which consists of two spaced perforated plates 26 formed of plastic or the like are suitably spaced and secured to the wall of the chamber, and have a suitable desiccant such as small particles of silica gel disposed therebetween. It is evident that the number and spacing of the drying units is a matter of choice, as well as the siZe of the desiccant particles in accordance with the desired operating characteristics of the device.

Disposed within the moistening chamber is a brush 30, the radially extending bristles of which extend substantially to the inner wall of the chamber. Shaft 31 of the brush extends longitudinally and is drivingly connected to electric motor 15. A reservoir of water or the like the upper surface of which is indicated by dotted line 32, is disposed in the lower portion of the moistening chamber and serves to moisten the bristles of the brush which is rotated during operation by electric motor 15.

The air passing through drying chamber 23 enters an antechamber 35 through opening 36, and the air passing through moistening chamber 24 enters an antechamber 37 through opening 38. Antechambers 35 and 37 face one another as more clearly seen in Fig. 2 and the walls thereof support circular segment bearing members 40 and 41 within which a cylindrical mixing valve 42 is rotatably mounted. Opposite ends of the mixing valve are sealed with respect to antechambers 35 and 37 by surrounding rings 45 and 46 which are secured to the walls of the antechambers and have a sealing fit with the outer surface of the mixing valve.

Cylindrical mixing valve 42 is hollow and is provided V 35, 37 and cavity 52.

' vide communication between antechambers 35, 37 and cavity 51. It should be noted that the openings and the adjacentbearing members 4%, 41 are so arranged that only five of the nine openings are uncovered at any one time and that the valve may be rotated in such a manner that various ratios may be obtained between the dry and moist air introduced into cavity 51. The amount'of air passing from either antechamber into cavity 51 may be varied from a maximum when all of the five uncovered openings 55 are in'comniunication with one of the chambers to a minimum when none of the openings are in communication with said one of the chambers and consequently there is no air flow therefrom. With the arrangement shown, six diiierent ratios of dry, to moist air may be obtained thereby afiording six degrees of humidity.

A second plurality of cylindrical openings 56, also nine in number and lying in a second cross-sectional plane spaced from that of openings 55 are formed through the valve and provide communication between antechambers In the example shown, cavity 52 is in communication with the atmosphere, although it may also be in communication with a second outlet conduit similar to conduit 53 if desired. As seen in Fig. 2, openings 56 are disposed oppositely to openings 55 in the valve and are complementary thereto. In other words, the two sets of openings are so arranged that five openings are always in communication with each of the antechambers, although the number of openings into either of cavities 51 or 52 from the opposite antechambers are different. In this manner, the degrees of humidity are adjustable while the total number of openings communicative with either of the antechambers is constant at all times thereby insuring a constant air flow throughthe drying and moistening chambers. A simple manually operable'handle 60 is provided such that it is readily accessible from the exterior of the apparatus for rotating the mixing Valve to control the degree of humidity in the outlet conduit. e

It is apparent that the number, size and spacing of the openings through the mixing valve is a matter of choice depending on the various degrees of humidity desired. The openings may also be disposed in a number of difierent longitudinal or radial rows. It is apparent that the mixing valve may also be in other forms such as V planar, for example, as long as the principles of the invention are adhered to such that the number of openings in communication with either of the antechambers remains constant. The disclosed configuration of the mixing valve is considered preferable, however since the air rushing into cavity 51 from opposite sides of the valve provide an efficient mixing of the dry and moist air which is very important for proper functioning of the device.

To facilitate calibration procedures, it may also be desirable to maintain the temperature of the air passing through the drying and moistening chambers constant. The air passing through the drying chamber 23 tends to heat up, and accordingly suitable cooling means may be provided. Forexample, an additional conduit may be provided from opening 36 and passing through a suitable water reservoir before entering antechamber 35 whereby the air is cooled down. The air passing through the moistening chamber 24 tends to cool down, and consequently suitable heating means may be provided. For example, a simple electricalresistance heating element may be disposed in or adjacent to the water reservoir disposed within chamber 24 for, keeping the. water .and

7 Letters Patent is:

the air passing through the chamber at a constant temperature. Since the air flow through the drying and moistening chambers is constant at all times, the amount of heating or cooling required will also be constant, thereby requiring only a minimum of adjustments during operation. Furthermore, suitable valves may be provided at openings 21 and 22 for controlling the speed of air flow through the drying and moistening chambers.

The apparatus as disclosed is intended for operation at temperatures above the freezing point. a The arrangement wherein a water reservoir is employed in the moistening chamber cannot, of course, be employed when the device is operating below the freezing point. In such a case, the moistening chamber may be filled with pieces of ice, and the surrounding air must be at the same low temperature, being controlled by conventional means such as a low-temperature thermostat. The air may be dried by cooling it by means of carbon dioxide snow and then reheating it to the desired temperature.

It is apparent from the foregoing that there is provided a new and novel hygrostat device wherein the humidity of the outlet air may be quickly and etficiently adjusted. The adjustments required during operation of the device are reduced to a minimum and the apparatus is simple and inexpensive in construction, yet accurate and reliable in operation. V

- What 'is claimed as new and desired to be secured by a 1. Hygrostat apparatus comprising a drying chamber and a moistening chamber, a mixing valve, gas passages providing communication between each of said chambers and said mixing valve, outlet means disposed in communication with said mixing valve, a first plurality of openings formed through a portion of said mixing valve providing communication between said drying chamber and said outlet means and between said moistening chamber and said outlet means, a second plurality of openings formed through another portion of said mixing valve and providing communication between said other portion and each of said chambers, means for varying the number of said first plurality of openings in communication with either said drying chamber or said moistening chamber, the total number of openings in communication with either said drying chamber or said moistening chamber always remaining equal, and means for urging a gaseous medium through said chambers and into said outlet means. a v

2. A device as defined in claim 1 wherein said mixing valve is constructed and arranged such that when the number of said first plurality of openings in communication with said drying chamber is increased, the number of said first plurality of openings in communication with said moistening chamber is decreased, and when the number of said first plurality of openings in communication with said drying chamber is decreased, the number of said first plurality of openings in communication with said moistening chamber is increased. a

3. A device as'defined in claim 2 whereinthe total number of said first plurality of openingsactually in communication with said outlet means is-constant.

4. Hygrostat apparatus as defined in claim 1 wherein said drying chamber includes desiccant meansdisposed across substantially an entire cross-sectional area of said chamber. 7

5. Hygrostat apparatus as defined in claim 1, wherein said moistening chamber includes brush means, a fiuidreservoir, and means for rotatingsaid brushmeanssuch that successive portions of said brush means pass through said fluid reservoir.v V

6. Hygrostat apparatus comprising a drying chamber and a moistening chamber, a mixingvalve, gas passages providing-comunication between each of said chambers and said mixing valve, a mixingcavity defined within said mixing valve, outlet meansdisposed in communciation with said mixing cavity, a first plurality of openings formed through a portion of said mixing valve providing communication between said drying chamber and said cavity and between said moistening chamber and said cavity, a second plurality of openings formed through another portion of said mixing valve and providing communication between said other portion and each of said chambers, said second plurality of openings being oppositely disposed to said first plurality of openings in said mixing valve, means for varying the number of said first plurality of openings in communication with either said drying chamber or said moistening chamber the total number of openings in communication with either said drying chamber or said moistening chamber always remaining equal, and means for urging a gaseous medium through said chambers and into said outlet means.

7. A device as defined in claim 6 wherein said mixing valve also defines a second cavity, said second plurality of openings providing communication between said second cavity and said drying chamber and between said second cavity and said moistening chamber.

No references cited. 

